This topic will discuss structural abnormalities of the umbilical cord that may be identified during a prenatal ultrasound examination, including their potential clinical significance and management of affected pregnancies. Postnatal examination of the umbilical cord is reviewed separately.

The umbilical cord contains two arteries and one vein surrounded by a gelatinous stroma (ie, Wharton's jelly) and covered by a single layer of amnion.

The left and right umbilical arteries are branches of the left and right internal iliac arteries, respectively. In the pelvis, the two arteries are separated by the bladder but then lie adjacent to each other at the umbilicus, where they exit the fetus and enter the umbilical cord (figure 1). The arteries follow a helical course around the umbilical vein until reaching the placenta, where they separate again and form the chorionic arteries on the surface of the placenta, with perforating branches to the underlying villi (figure 2).

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American Institute of Ultrasound in Medicine. AIUM practice parameter for the performance of obstetric ultrasound examinations. Renamed 2015. http://www.aium.org/resources/guidelines/obstetric.pdf (Accessed on May 05, 2016).